Filaments



Feb. 9, 1965 w. B. MILLER ETAL 3,%9,9

FILAMENTS Filed April 22. 1960 FILAMENTS William Burton Miller,Pearishurg, and Clarence Edward Eishop, Narrows, Va, assignors toCelanese Corporation of America, New York, N.Y., a corporation ofDelaware Filed Apr. 22, 1960, Ser. No. 24,025 3 Claims. (Cl. 161-477)the production of filamentary material of the aforesaid type.

Still another object of the present invention is to provide yarns orfilamentary material affording, for a given denier, a larger surfacearea, superior bulking properties and a higher beam strength thanbulbous filaments dry spun through circular orifices.

A further object of the filamentary material of the aforesaid type whichdoes not pack tightly and exhibits improved resilience, air permeabilityand filtering power for its denier as compared with conventionalfilaments, whereby it is particularly suited not only for use in themanufacture of carpeting, upholstery, drape and other textile fabricsbut also for use as cigarette filters and such non-textile materials aspadding or filling.

A related object of the present invention is to provide such filamentarymaterial which is composed of a blend or mixture of individual filamentsof diiferent crossscctional shapes.

Concurrently, therefore, it is also an object of the present inventionto provide novel spinnerettes each having a plurality of jet openings,with the configurations of one set of such openings ditfering from theconfigurations of another set of said openings, so as to produce theabovedescribed blend of cross-sectional shapes.

The foregoing and other objects, characteristics and advantages of thepresent invention will be more fully understood from the followingdetailed description thereof when read in conjunction with theaccompanying drawing, in which:

FIG. 1 is a plan view of a spinnerette constructed with a plurality ofjet openings specially shaped according to one embodiment of the presentinvention;

FIG. 2 is a cross-sectional view, on an enlarged scale, of thefilamentary material produced by means of a spinnerette having jetopenings as shown in FIG. 1;

FIG. 3 is a graphic representation of the manner of construction anddimensioning of the jet openings shown in FIG. 1;

FIG. 4 is a plan view of a spinnerette having jet openings of the typeshown in FIG. 1 alternating with circular jet openings; and

FIG. 5 is a cross-sectional view, on an enlarged scale, of the blend offilaments produced by means of the spinnerette of FIG. 4.

In accordance with the invention generally, filamentforming material inliquid phase, e.g. a solution in a volatile solvent, is dry spun byextrusion through the openings or orifices of a spinnerette into anevaporative atmosphere or heated air. A dry spinning system equippedwith such a spinnerette for converting derivatives of celpresentinvention is to provide lulose, more particularly a cellulose organicacid ester solution such as cellulose acetate in a volatile solvent,into filaments, yarn or tow is well known and need not be illustrated ordescribed in detail herein.

According to the present invention, there is provided a novelspinnerette having a plurality of jet openings-each of which is shapedsubstantially in the form of a cross defined by a large square outof'the corners of which there are removed small squares the sides ofwhich range from about 20 to 30% and preferably about 24 to 28% of thesides of the largesquare. The cross-sectional shapes of the filamentsproduced by means of such jet openings resemble four-leaf clovers orshamrocks.

In accordance with a modification of the invention, the aforesaid jetopenings are alternated with jet openings having different shapes, suchas circles, semicircles, crescents and the like. Although the jetopenings are shown in the drawing as being oriented in their respectivespin nerettes in a predetermined manner, it will be understood thatthese openings may be oriented differently with respect to one anotherand to the outer periphery of the spinnerette.

Filamentary materials in accordance with the present invention maycomprise organic derivatives of cellulose such as the esters or ethersthereof, for example, cellulose organic acid esters such as celluloseacetate, cellulose propionate, cellulose butyrate, cellulose benzoate,cellulose acetate formate, cellulose acetate propionate, celluloseacetate butyrate, and the like, ethyl cellulose, etc. The esters may beripened and acetone-soluble, such as conventional cellulose acetate, ormay be substantially fully esterified, that is, contain fewer than 0.29free hydroxyl groups per anhydroglucose unit, e.g. cellulose triacetate.

The filament-forrning material may also comprise other thermoplastic orsolvent-soluble polymeric materials such as superpolyamides, e.g. nylon,superpolyesters such as polyethylene terephthalate, polyglycolic acidand copolymers thereof, acrylonitrile polymers and copolymers, polymersand copolymers of vinylidene compounds such as ethylene, propylene,vinylchloride, vinylidene chloride, acrylonitrile, vinylidene cyanide,vinyl acetate, and the like.

The filament-forming material is initially in liquid phase. Inoperation, a solution of the filament-forming material in a volatilesolvent is extruded through the jet openings of a spinnerette into anevaporative atmosphere. The filaments formed upon extrusion of thesolution are taken up at a linear speed ranging from about meters perminute to about 900 meters per minute and preferably from about 200meters per minute to about 600 meters per minute. The ratio of thetake-up speed to the linear speed at which the solution is extrudedthrough the jet openings, i.e. the drawdown ratio, may range from about0.6 to 2.0 and preferably ranges from about 0.8 to about 1.6. When dryspinning a solution of secondary cellulose acetate in acetone, thetemperature of the dope being extruded generally ranges from about 40 C.to about C. and preferably from about 60 C. to about 85 C.

In forming filaments in accordance with the present invention, eachspinnerette may be provided with as many as 300 or more jet openings ororifices. The denier per filament may be 55 or more, but generallyranges from about 2 to 25 and preferably from about 3 to 20. The spunfilaments can be collected into yarn ends having the desired number offilaments. When necessary, large bundles or tows of filaments can beformed directly from the spun filaments, or alternatively by combiningseveral smaller bundles of spun filaments, for facilitating theformation of staple fibers by cutting. Prior to any processingsubsequent to the extrusion, the filaments as a unit may be subjected toany desired volumnizing treatment to increase the bulk thereof, as bycrimping, eg to impart about to 20 and preferably 7 to 12 crimps perinch.

Referring now more particularly to FIG. 1, it will be seen that thespinnerette 10 according to the present invention is provided with aplurality of jet openings 11 each of which is shaped substantially inthe form of a special cross.

The formation, dimensioning and other structural characteristics of thejet openings 11 may be somewhat better understood by reference to FIG. 3which shows, on a greatly enlarged scale, a graphical representation ofsuch an opening and its relationship to its circumscribed square andcircle. As can be seen in FIG. 3, the shape of the cross-like polygonAB-CD-E-F-G-H JKL-MA illustrated in solid lines corresponds to that ofany of the openings 11 shown in FIG. 1. There are also shown points N,O, P, Q and dotted lines connecting these points to the cross-shapedopening. The points N, O, P, Q define a large square; the cross-shapedopening A-BCD-EFGH-]KL-M- A is the result of removing from each cornerof large square N-O-PQ a small square, e.g. LM--AQ, the sides of whichrange from about 20 to 30% and preferably about 24 to 28% of the lengthof the sides of the large square. While illustrated as straight, linesA-B, D-E, 6-H and K-L might be slightly bowed or arcuatc as would occurif the basic shape from which the small squares were cut out were acircle rather than a large square.

As previously intimated, the number of jet openings or holes 11 may bequite high and it is, therefore, apparent that the locus of all the jetopenings in the spinnerette 10 need not be one circle, as indicated inbroken lines in FIG. 1. Merely by way of example, the loci of thedifferent sets of jet openings 11 may be a plurality of concentriccircles. Moreover, although with the openings as illustrated one of theaxes of each opening is oriented radially of the spinnerette, it is tobe understood that in accordance with the present invention other,possibly random and certainly not necessarily uniform, orientations ofthe axes of the jet openings are possible. Referring now to FIG. 2, itwill be seen that the yarn or filamentary material produced by extrusionof the filament-forming substance through the spinnerette 10 is composedof a bundle of filaments 20 which resemble, in cross-sectional shape,four-leaf clovers or Shamrocks. Thus, each filament 20 has a core 20aand four lobelike arms 20b, 20c, 20d and 20.2 extending from the core.The cross-sectional periphery, and hence the filament surface area ofeach of the novel filaments 20 is about 10% to 50% greater than that ofa filament of equal denier spun through a circular jet opening andhaving a bulbous cross-section. The filaments 20, moreover, have aconsiderably greater beam strength and elasticity than filaments ofbulbous, or similar cross-sectional shapes and also have good bulkingproperties, while fabrics produced from such filaments exhibit theadvantageous property of high dye absorbency and are also characterizedby high tenacity, elongation, bulk and abrasion resistance. Suchfabrics, furthermore, are thick and of relatively low compressibilityand are characterized by high air permeability. The filaments are alsocharacterized by marked crosssection fidelity, i.e. substantialuniformity, along each filament and from filament to filament.

Referring now to FIGS. 4 and 5, the spinnerette 21 shown in FIG. 4differs from the spinnerette 10 in that the substantially cross-shapedjet openings 11 are arranged in alternating sequence with other jetopenings having different cross-sectional shapes. More specifically, inthe spinnerette 21 the jet openings 11 alternate with circular jetopenings 22, but it will be understood that the jet openings 11 can bealternated with jet openings of dillerent shapes, such as semicircles,crescents, etc.

The yarn formed by the extrusion of the filament-forming materialthrough the spinnerette 21 is illustrated in FIG. 5. As shown there, theyarn produced by means of the spinnerette 21 is composed of a mixture orblend of the substantially four-leaf clover or lobed filaments 2% withfilaments 23 being formed from the material extruded through thecircular jet openings 22.

As hereinbeforc stated, the yarns produced in accordance with thepresent invention are capable of being used in a variety of ways. Inparticular, blends or mixturcs of filaments such as 20-23 may beespecially advantageously employed in the manufacture of cigarettefilters (not shown), inasmuch as these blends of filaments do not packtoo tightly, thereby retaining their high air permeability and ease ofdrawing while being characterized by a relatively great filteringcapacity.

The following examples will serve to illustrate the principles of thepresent invention more clearly.

Example I An acetone solution of secondary cellulose acetate having anacetyl value of 55% is extruded at a linear speed of 250 meters perminute through a spinnerette provided with 200 jet openings each havingthe shape of a cross-like polygon as shown in FIG. 1. The length of eachof the sides of the large square is 0.058 mm, and the length of each ofthe sides of the small squares is 0.016 mm. The temperature of the dopeat the jet face is approximately 65 C. The filaments are withdrawn at adrawdown ratio of 1.10. Upon analysis, the resulting yarn is found tohave a denier of 1,000, i.e., a denier per filament of about 5.0, and isshaped in cross-section as shown in FIG. 2. The filaments have arelatively great beam strength and are also characterized by a highresistance to abrasion and by even dyeing.

70 such bundles of filaments can be gathered into a tow, crimped toimpart about 8 crimps per inch, opened, sprayed to pick up about 6% byweight of glycerine triacetate, wrapped with paper, out intopredetermined lengths, cured and incorporated into cigarettes as filtertips.

Example 11 The procedure set forth in Example I is repeated, using aspinnerette provided with jet openings each having the shape of across-like polygon as shown in FIG. 1 and alternating with 75 jetopenings of circular shape, in the manner illustrated in FIG. 4. Theyarn is extracted from the metier at a drawdown ratio of about 1.0.

It is to be understood that the foregoing detailed description is givenmerely by way of illustration and that many variations may be made inthe invention without departing from the spirit thereof.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:

1. Filamentary material having a four-leaf clover crosssection which issubstantially uniform along the length of the filamentary material, saidcross-section including four substantially smooth rounded lobesextending independently and substantially symmetrically from a centralcore, each of said lobes being narrowest where it is joined to said coreand having its maximum width nearer to the outermost extremity of saidlobe than to said core and continuously increasing in Width from saidnarrowest portion to said maximum width, said lobes completelysurrounding said core except for the narrow radial spaces, of lesserwidth than said lobes, between said lobes.

2. Filamentary material according to claim 1, comprising celluloseacetate.

3. Filamentary material comprising a plurality of filaments havingfour-leaf clover cross-sections which are References eaea in the file ofthis patent substantially uniform along each filament and amongst V theseveral filaments of such cross-section, sm'd cross-section includingfour substantially smooth rounded lobes extending independently andsubstantially symmetrically from a central core, each of said lobesbeing narrowest Where it is joined to said core and having its maximumwidth nearer to the outermost extremity of said lobe than to said coreand continuously increasing in width from said narrowest portion to saidmaximum Width, said lobes completely surrounding said core except forthe narrow radial spaces, of lesser width than said lobes, between saidlobes.

UNITED STATES PATENTS Dreyfus Aug. 26, Thenoz Ian. 23, Marshall .ay 23,White a- June 19, Wi liams Nov. 20, Holland June 7, Holland June 7,Swerdloff, et al. Jan. 24,

OTHER REFERENCES Erith: White Clover-A Monograph, Duckworth 15 and Co.,1924, London (pp. 37 and 121 of interest only).

1. FILAMENTARY MATERIAL HAVING A FOUR-LEAF CLOVER CROSSSECTION WHICH ISSUBSTANTIALLY UNIFORM ALONG THE LENGTH OF THE FILAMENTARY MATERIAL, SAIDCROSS-SECTION INCLUDING FOUR SUBSTANTIALLY SMOOTH ROUNDED LOBESEXTENDING INDEPENDENTLY AND SUBSTANTIALLY SYMMETRICALLY FROM A CENTRALCORE, EACH OF SAID LOBES BEING NARROWEST WHERE IT IS JOINED TO SAID COREAND HAVING ITS MACIMUM WIDTH NEARER TO THE OUTERMOST EXTREMITY OF SAIDLOBE THAN TO SAID CORE AND CONTINUOUSLY INCREASING IN WIDTH FROM SAIDNARROWEST PORTION TO SAID MAXIMUM WIDTH, SAID LOBES COMPLETELYSURROUNDING SAID CORE EXCEPT FOR THE NARROW RADIAL SPACES, OF LESSERWIDTH THAN SAID LOBES, BETWEEN SAID LOBES.